Java设计模-过滤器模式

过滤器模式

过滤器模式（Filter Pattern）或标准模式（Criteria Pattern）是一种设计模式，这种模式允许开发人员使用不同的标准来过滤一组对象，通过逻辑运算以解耦的方式把它们连接起来。这种类型的设计模式属于结构型模式，它结合多个标准来获得单一标准。

实现

我们将创建一个 Person 对象、Criteria 接口和实现了该接口的实体类，来过滤 Person 对象的列表。CriteriaPatternDemo，我们的演示类使用 Criteria 对象，基于各种标准和它们的结合来过滤 Person 对象的列表。

步骤 1

创建一个类，在该类上应用标准。

Person.java

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public class Person {

private String name;

private String gender;

private String maritalStatus;

public Person(String name,String gender,String maritalStatus){

this.name = name;

this.gender = gender;

this.maritalStatus = maritalStatus;

}

public String getName() {

return name;

}

public String getGender() {

return gender;

}

public String getMaritalStatus() {

return maritalStatus;

}

步骤 2

为标准（Criteria）创建一个接口。

Criteria.java

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import java.util.List;

public interface Criteria {

public List<Person> meetCriteria(List<Person> persons);

}

步骤 3

创建实现了 Criteria 接口的实体类。

CriteriaMale.java

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import java.util.ArrayList;

import java.util.List;

public class CriteriaMale implements Criteria {

@Override

public List<Person> meetCriteria(List<Person> persons) {

List<Person> malePersons = new ArrayList<Person>();

for (Person person : persons) {

if(person.getGender().equalsIgnoreCase("MALE")){

malePersons.add(person);

}

return malePersons;

}

CriteriaFemale.java

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import java.util.ArrayList;

import java.util.List;

public class CriteriaFemale implements Criteria {

@Override

public List<Person> meetCriteria(List<Person> persons) {

List<Person> femalePersons = new ArrayList<Person>();

for (Person person : persons) {

if(person.getGender().equalsIgnoreCase("FEMALE")){

femalePersons.add(person);

}

return femalePersons;

}

CriteriaSingle.java

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import java.util.ArrayList;

import java.util.List;

public class CriteriaSingle implements Criteria {

@Override

public List<Person> meetCriteria(List<Person> persons) {

List<Person> singlePersons = new ArrayList<Person>();

for (Person person : persons) {

if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){

singlePersons.add(person);

}

return singlePersons;

}

AndCriteria.java

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import java.util.List;

public class AndCriteria implements Criteria {

private Criteria criteria;

private Criteria otherCriteria;

public AndCriteria(Criteria criteria, Criteria otherCriteria) {

this.criteria = criteria;

this.otherCriteria = otherCriteria;

}

@Override

public List<Person> meetCriteria(List<Person> persons) {

List<Person> firstCriteriaPersons = criteria.meetCriteria(persons);

return otherCriteria.meetCriteria(firstCriteriaPersons);

}

OrCriteria.java

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import java.util.List;

public class OrCriteria implements Criteria {

private Criteria criteria;

private Criteria otherCriteria;

public OrCriteria(Criteria criteria, Criteria otherCriteria) {

this.criteria = criteria;

this.otherCriteria = otherCriteria;

}

@Override

public List<Person> meetCriteria(List<Person> persons) {

List<Person> firstCriteriaItems = criteria.meetCriteria(persons);

List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons);

for (Person person : otherCriteriaItems) {

if(!firstCriteriaItems.contains(person)){

firstCriteriaItems.add(person);

}

return firstCriteriaItems;

}

步骤4

使用不同的标准（Criteria）和它们的结合来过滤 Person 对象的列表。

CriteriaPatternDemo.java

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public class CriteriaPatternDemo {

public static void main(String[] args) {

List<Person> persons = new ArrayList<Person>();

persons.add(new Person("Robert","Male", "Single"));

persons.add(new Person("John","Male", "Married"));

persons.add(new Person("Laura","Female", "Married"));

persons.add(new Person("Diana","Female", "Single"));

persons.add(new Person("Mike","Male", "Single"));

persons.add(new Person("Bobby","Male", "Single"));

Criteria male = new CriteriaMale();

Criteria female = new CriteriaFemale();

Criteria single = new CriteriaSingle();

Criteria singleMale = new AndCriteria(single, male);

Criteria singleOrFemale = new OrCriteria(single, female);

System.out.println("Males: ");

printPersons(male.meetCriteria(persons));

System.out.println("\nFemales: ");

printPersons(female.meetCriteria(persons));

System.out.println("\nSingle Males: ");

printPersons(singleMale.meetCriteria(persons));

System.out.println("\nSingle Or Females: ");

printPersons(singleOrFemale.meetCriteria(persons));

}

public static void printPersons(List<Person> persons){

for (Person person : persons) {

System.out.println("Person : [ Name : " + person.getName()

+", Gender : " + person.getGender()

+", Marital Status : " + person.getMaritalStatus()

+" ]");

}

步骤 5

验证输出。

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Males:

Person : [ Name : Robert, Gender : Male, Marital Status : Single ]

Person : [ Name : John, Gender : Male, Marital Status : Married ]

Person : [ Name : Mike, Gender : Male, Marital Status : Single ]

Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]

Females:

Person : [ Name : Laura, Gender : Female, Marital Status : Married ]

Person : [ Name : Diana, Gender : Female, Marital Status : Single ]

Single Males:

Person : [ Name : Robert, Gender : Male, Marital Status : Single ]

Person : [ Name : Mike, Gender : Male, Marital Status : Single ]

Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]

Single Or Females:

Person : [ Name : Robert, Gender : Male, Marital Status : Single ]

Person : [ Name : Diana, Gender : Female, Marital Status : Single ]

Person : [ Name : Mike, Gender : Male, Marital Status : Single ]

Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]

Person : [ Name : Laura, Gender : Female, Marital Status : Married ]